Two temperature refrigeration apparatus



1949- L. B. M. BUCHANAN 2,458,560

TWO TEMPERATURE REFRIGERAT I ON APPARATUS Filed Aug. 15, 1946 WITNESSES INVENTOR Y I 1,551.15: 5. M. BUCHANAN.

ATTORNEY Patented Jan. 11, 1949 TWO TEIHPERATURE REFRIGERATION APPARATUS Leslie B. M. Buchanan,

signor to Westinghous East Pittsburgh, Pa.,

vania Springfield, Mass., as-

e Electric Corporation, corporation of Pennsyl- Application August 13, 1846, Serial No. 690,158

This invention relates to refrigeration apparatus of the compressor-condenser-capillary tubeevaporator type, and more especially to a means for distributing the refrigerant circulated by a single compressor to two or more evaporators connected in parallel.

When supplying refrigerant to two evaporators connected in parallel in such a system, a diflieulty arises in the proper proportioning of the refrigerant to the two evaporators. It is desirable, for purposes of regulation, to pass a small quantity of refrigerant vapor with the liquid refrigerant from the condenser into the capillary tube during certain conditions of load.

Where a difference in the refrigerant level or in the suction pressure on the two evaporators is to be maintained, a separate capillary tube is used for each evaporator. These tubes are customarily connected to one condenser. In such a system, the problem consists not only in apportioning the refrigerant liquid to the two capillary tubes in the proper ratio but also in apportioning the refrigerant vapor to these tubes. capillary tube for a domestic refrigerator is about .03 of an inch in diameter, this apportionment is It is, accordingly, an object of this invention to provide a novel means for operating two or more evaporators in parallel from a common source of compressed refrigerant vapor while using only capillary tubes as flow-impeding devices.

It is a further object of the invention to utilize a single compressor and capillary tubes for operating two evaporators in parallel.

These and other objects are effected by the invention as will be apparent from the following description and claims taken in connection with the accompanying drawings, forming a part of this application, in which:

Fig. 1 isa schematic drawing of the refrigerating apparatus of this invention; and

Fig. 2 is an enlarged sectional view of the upper portion of the refrigerant compressor of Fig. 1.

Referring to the drawings, the'reference numeral I 8 designates a reciprocating compressor driven by an electric motor I2. The compressor l includes a reciprocating piston l4, a main inlet port 16, an auxiliary inlet port l8 and an exhaust port 28. The compressed vapor from the exhaust port 20 passes through the exhaust valve 22 into the pressure conduit 24 which communicates with Since the bore of a 7 Claims. (01. 62-3) to a low temperature evaporator 32 wherein the refrigerant liquid is vaporized at a low suction pressure and then passes through a suction tube 34 to the main inlet port I 8. The refrigerant liquid condensed in the condenser 26 passes through a capillary tube 36 to a higher temperature evaporator 38 in which the refrigerant liquid is vaporized at a higher suction pressure and thereupon passes through a suction tube 48 to the auxiliary inlet port l8.

When the piston M of the compresser In descends from its uppermost position, a suction is created in the cylinder 42 of the compressor l0 and a suction valve 44 opens to admit refrigerant vapor from the suction conduit 34 to the cylinder 42. As the piston l4 uncovers the auxiliary inlet port I8, refrigerant vapor from the higher temperature evaporator 38 is drawn into the cylinder 42 to relieve the low suction pressure therein and valve 44 closes. On the upstroke of the piston l4,

. the inlet port I 8 is covered by the piston l4 and the vapor in the cylinder 42 is forced through the exhaust port 20 into the pressure conduit 24.

The low temperature evaporator 32 is enclosed in an insulated cabinet simulated by the dotted lines 46 to form a low temperature compartment such as used for storing frozen foods. The higher temperature evaporator 38 is enclosed by a second insulated cabinet simulated by the dotted lines 48, which provides a higher temperature food storage cabinetfor the storage of unfrozen cothe two air-cooled condensers 28 and 28 wherein mestibles.

The electric motor I2 receives power from the lines 58 through leads 52 and 54. A temperaturecontrolling switch 58 is located in lead 54 and is actuated through. a snap-acting device 58 by the bellows 60. through a tube 62 with a bulb 84 which contains a volatile fluid and is located in the insulated cabinet 48. The vapor pressure of this fluid is responsive to the temperature of the cabinet 48 and opens and closes the switch 56 to maintain the temperature of the cabinet 48 between pre-.

determined limits, as is well understood in the art.

The condenser 26 is cooled by a fan 88 driven by an electric motor 68 whichmay be connected through a variable speed rheostat Ill to leads 12 to operate in parallel with the motor l2. The condenser 28 is similarly cooled by a fan 12 driven by an electric motor 14 which may be energized through a variable speed regulating rheostat 18 from leads 18 to operate in parallel with the motor l2.

The system is preferably so proportioned that The bellows communicates- 3 atleasttowardstheendofeachperiodofoperatimi of the compressor, at least one of the'condensers retains no refrigerant liquid, the liquid which is being condensed passing immediately intotheca illarytubetogetherwithasmall quantity of refrigerant vapor. If it is now desired toincreaseflieflowofrdrigerantlimzidtothe evaporator asociated with this condenser, the flowofcoolingalrtothecondenserisincreased, thereby increasing the rate of condensation of the The additional refrigerant liquid willreplacesomeoralloftherefrigerantvapor formerly flowing into the capillary tube and will enter the evaporator.

Iftheflowofairthroughthecondenserisstill furtherincreaseithefiowofrefrigerantthrough the capillary tube cmnected with the condenser also will be still further increased. This is caused by the fact that refrigerant liquid will be present in the during the operating period of the compresor. The'liquid willbe sub-cooled and will enter the capillary tube at a lower temperature than formerly. This will retard the formation of refrigerant vapor in the capillary tube and thereby allow more refrigerant liquid to flow through it into the evaporator.

The invention has been described in connection with an apparatus having two evaporators operated at different suction pressures by a ported compressor. It is equally applicable to evaporators operated at the same suction pressure in which case the auxiliary port ll of the compressor would be eliminated and the evaporator 38 would be connected to the suction conduit 34 in parallel with the evaporator 32.

While the invention has been shown in but one form, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various changes and modifications without departing from the spirit thereof.

What is claimed is:

1. In refrigerating apparatus including refrigerant vapor compressing means and two evaporators connected to the inlet means of said compressing means, the combination with said evaporators of two condensers connected in parallel to the outlet means of said compressing means and two capillary flow-impeding tubes, one of 4 said tubes conducting refrigerant from only one of said condensers to only one of said evaporators and the other of said tubes conducting refrigerant from only the other of said condensers to only the other of said evaporators.

2. The refrigerating apparatus according to claim 1 including means for varying the refrigerant condensing rate of at least one of said condensers.

3. The refrigerating apparatus defined in claim 1 including means for varying the refrigerant condensing rate of both of said condensers.

4. The refrigerating apparatus defined in claim 1 including means for circulating a cooling medium through each of said condensers and means for varying the rate of flow of the cooling medium through at least one of said condensers.

5. The refrigerating apparatus defined in claim 1 in which at least one of said capillary flow-impeding tubes is of such low impedance that it allows both refrigerant liquid and refrigerant vapor to pass from one of said condensers to one of said evaporators.

6. In refrigerating apparatus including a compressor having a. low pressure inlet port, a higher pressure inlet port, and an exhaust port, a first evaporator connected to said low pressure port, a second evaporator connected to said higher pressure port, the combination with said evaporators of a first condenser connected to said exhaust port, a second condenser connected in parallel to said first-named condenser to said exhaust port, a first capillary flow-impeding tube for conducting refrigerant from only said first condenser to only said first evaporator, and a second capillary flow-impeding tube for conducting refrigerant from only said second condenser to only said second evaporator.

7. The refrigerating apparatus defined in claim 5 including means for varying the refrigerant No references cited. 

